Exhaust gas recirculation (EGR) is used to reduce emissions and increase fuel economy in internal combustion engines. Exhaust gas is forced from the engine cylinders into the exhaust manifold after combustion. The exhaust gas includes non-burnable gas and other emissions that are otherwise released into the environment.
Conventionally, EGR is used while the engine is running to reduce emissions and increase fuel economy. The exhaust gas is recirculated to mix with intake air before entering the engine cylinders. Because the recirculated exhaust gas is non-burnable and displaces a portion of the intake air, a smaller amount of burnable intake air enters the engine. Therefore, a smaller amount of fuel is required to combust with the burnable air.